Get some cotton cheesecloth. It's very important that the cheesecloth isn't made from a synthetic fiber. After seasoning and optionally stuffing the turkey, spread the cheesecloth 2 layers thick over the breast. Make up a basting solution from a melted stick of butter and some dry white wine. Drench the cheesecloth with the butter/wine mixture. Sear the turkey at 400° for the first half hour of cooking, then ramp the oven down to 350° for the remainder of the required cooking time. Redrench the cheesecloth with the wine/butter mixture every half hour. This will keep the temperature of the breast meat lower than the dark meat. This is the real secret of this method. The breast meat will be fully cooked when it reaches 140°. The dark meat requires 170°. If you run out of the butter/wine mixture, just switch to basting with water.

Once the thigh tests at 160°, remove the cheesecloth, and cook for 30 minutes more. Remove the turkey from the oven, cover with foil, and let the turkey rest for at least 30 minutes. If you slice the turkey fresh out of the oven, no amount of preparation will prevent the juice from running out.

Other tricks for tasty turkey:
Cover the skin of the turkey with a thick layer of koshersea salt for a few hours before cooking.
When ready to cook, brush off the salt and place pats of butter under the turkey skin.
Cover the turkey with an aluminium foil tent during the begining of cooking, remove it for the last 30 minutes to brown the skin.

One particularly hectic Thanksgiving when my mother was running around trying to get everything ready, guests collected, side dishes completed and all the other zillion things that come with cooking your own Thanksgiving meal, she made one simple error that no one caught until we were all primped and dressed nicely and sitting at the dinner table with our guests. The foil cooking tent was removed from the masterpiece of the turkey, and my father was prepared to carve it, when he realized he didn't quite understand what he was looking at. It took us all a minute more of confusion to realize that the bird had been put in the oven upside down, laying on the breast with the wings and legs facing skyward.

After some nervous laughter and my mother's worries that it would turn out horribly becuase she'd done something so silly, we carved the bird anyways and passed plates full of meat around the table. It was, hands down, the tenderest turkey any of us had ever eaten.

Come Christmas, there was another turkey, cooked correctly. It wasn't nearly as juicy or tender as the first. So the next year, it was cooked upside down again and came out just as juicy and flavorful. Now, unless one of us forgets, our turkeys are almost always cooked upside down.

If you ever do try this, by accident or design, I'd love to hear how it turns out. But do remember this is anecdotal evidence from one family and you may not want to try this with a hungry dinner party waiting on you, just in case. yclept and demeter have informed me that this is acutally a well-recognised technique among chefs and those who prepare lots of poultry and is in fact considered the "proper" way to cook whole birds. It's just not done so often because it doesn't look quite as pretty and it doesn't sit in the pan as well. It works for more or less the reasons I assumed. The dark meat can get hotter when it's on top and exposed and the breast stay cooler because the pan protects it. Also the fat and juices sort of self-baste the turkey and since the breast is now sitting in this liquid, it stays moister. Thanks guys.